1. Field of the Invention
The present invention relates to an LED (Light Emitting Diode) short-circuit detection circuit, an LED drive circuit, an LED lighting device, and a vehicle that use the LED short-circuit detection circuit.
2. Description of Related Art
In a case where a plurality of LEDs are connected in series and are driven, when the LED shorts on one stage, the number of turned-on LEDs decreases by one stage and the brightness of the LED line becomes low as a whole. Especially, in the field of a vehicle lamp, because a brightness shortage is handled as a violation of the law, an LED short-circuit detection circuit is a must.
FIG. 24 is a circuit diagram showing a conventional example of the LED short-circuit detection circuit. The LED short-circuit detection circuit as the conventional example has a structure which uses an external discrete component to compare an output voltage Vout applied to an anode of the LED line and a predetermined detection voltage Vth with each other in absolute value, thereby generating an LED short-circuit detection signal.
Here, as an example of the conventional technology related to the above description, there is JP-A-2008-084614.
However, in the LED short-circuit detection circuit as the conventional example, adjustment of the detection voltage Vth must be performed considering unevenness of a forward drop voltage VF and a temperature characteristic of the LED, so that there is a problem that a management burden during a production process is large.
Besides, in the LED short-circuit detection circuit as the conventional example, to mount the LED short-circuit detection circuit, many external discrete components are necessary, which brings a problem that a board area becomes large.
Here, when the LED short-circuit detection circuit as the conventional example is simply integrated, there is a problem that the adjustment of the detection voltage Vth becomes hard; and the LED short-circuit detection accuracy deteriorates.